Starting Onions from Seed

Although onions may seem like a fairly cheap “staple” vegetable not worthy of a spot in the urban garden, the truth is- they are one of the easiest vegetables to grow. Onions have few pests/diseases in our area and they require little maintenance other than watering to yield large, perfect bulbs. The 3-4 types of onions you typically see in the grocery store are only a fraction of the delicious varieties available. Late February/early March in Chicagoland is the perfect time to start onions from seed.

This onion isn't quite ready for harvest, but will be in a few weeks.

‘Yellow of Parma’ onion.

As with starting other seeds indoors, follow these tips for success:

-Use a store-bought or homemade seed starting mix (not potting soil, garden soil, or 100% compost).
Moisten your seed starting mix prior to filling cells, shaping blocks, or filling a tray.
-Plant your seeds at the correct depth. For onions, this will be about 1/4″.
-Keep seed starting mix moist: water from the bottom, and keep a plastic dome or plastic wrap on the surface until germination.
-Place your seed starting tray in a warm spot. This could be on top of a seedling heat mat, cabinet or refrigerator. Once the seeds have germinated, remove from the heat source. Germination may take 4-16 days, depending on soil temperature and onion variety. 
-After germination, direct bright light is critical for strong growth.
Transplant outdoors after about a week of hardening off, when nighttime temperatures are no lower than about 50F. This is usually around late April in Chicagoland.

written by Breanne Heath